1. Field of the Invention
The present invention generally relates to an apparatus for drying a semiconductor wafer, and more particularly, to an apparatus for drying a semiconductor wafer using an isopropyl alcohol (IPA) vapor drying method.
2. Description of the Related Art
In general, a cleaning process of a semiconductor chip includes the removal of impurities generated on a semiconductor wafer during a manufacturing process. The cleaning process may include processing the semiconductor wafer using chemical solutions, rinsing the chemically processed semiconductor wafer using deionized water (DIW), and drying the rinsed semiconductor wafer.
In the prior art, a spin drying method is commonly used to dry a semiconductor wafer. Recently, due to an increase in an integration density of semiconductor devices, a vapor drying method has been used. The vapor drying method takes uses isopropyl alcohol (IPA) vapor to remove the DIW.
In a conventional apparatus for drying semiconductor wafers, semiconductor wafers are loaded in a chamber and an IPA solution is supplied into the chamber. The IPA solution supplied into the chamber is vaporized by heat produced by a heater positioned under the chamber. As the IPA solution is vaporized, the DIW remaining on the semiconductor wafers substantially removed.
The conventional apparatus for drying semiconductor wafers cannot precisely control the degree at which the IPA solution is vaporized. If the IPA solution is excessively vaporized in the chamber, a considerable amount of carbon (C) remains on the surfaces of the dried semiconductor wafers.
Recently, an apparatus for drying semiconductor wafers using IPA vapor, which includes an integrated bath and chamber, has been suggested. According to this apparatus, during a drying process DIW overflows the bath, and nitrogen gas and IPA vapor can be supplied to the chamber. More particularly, a drying process according to the apparatus is performed as follows. The bath, in which a semiconductor wafer is loaded, is made to overflow with DIW, and then nitrogen gas and IPA vapor are supplied from above the semiconductor wafer into the chamber. Simultaneously, the DIW is slowly discharged toward a lower part of the semiconductor wafer.
FIG. 1 is a cross-sectional view of a conventional apparatus for drying semiconductor wafers using a conventional IPA vapor drying method according to an exemplary embodiment of the present invention. Referring to FIG. 1, the apparatus for drying semiconductor wafers includes a bath 200, which is provided so that a semiconductor wafer 100 can soak in DIW 210. In addition, a chamber 300 is included, which surrounds the bath 200 and overlaps an upper part of the bath 200.
The bath 200 includes a DIW outlet 220, through which the DIW 210 can drain. A semiconductor wafer supporter 230 is arranged under the semiconductor wafer 100 to support the semiconductor wafer 100. Guides are formed on the surface of the semiconductor wafer supporter 230 facing the semiconductor wafer 100. The structure of the guides will be described in greater detail hereinafter.
A pipeline 312 for supplying nitrogen gas and/or, a pipeline 314 for supplying nitrogen gas and IPA vapor, and a pipeline 320, through which overflowed DIW drains, are connected to the chamber 300. An outlet 330, through which nitrogen gas and IPA vapor in the chamber 300 drain to the outside, is provided through a sidewall of the chamber 300.
FIG. 2A is a diagram illustrating guides formed on the semiconductor wafer supporter 230 of the apparatus for drying semiconductor wafers shown in FIG. 1. FIG. 2B is a cross-sectional view taken along line 2B-2B′ of FIG. 2A and as seen from a direction indicated by A. Referring to FIGS. 2A and 2B, three guides, i.e., first, second, and third guides 231, 232, and 233, are formed on the surface of the semiconductor wafer supporter 230 facing the semiconductor wafer 100. The first and second guides 231 and 232 are formed to have a substantially V-shaped groove so that the semiconductor wafer 100 can be inserted in the substantially V-shaped grooves of the first and second guides 231 and 232. When a drying process is performed with semiconductor wafers supported by the semiconductor wafer supporter 230 having the three guides 231, 232, and 233, adjacent semiconductor wafers may be attached to one another, as will be described in greater detail in the following paragraphs.
FIGS. 3A through 3D are diagrams illustrating a drying process performed in an apparatus for drying semiconductor wafers using a semiconductor wafer supporter having three guides. Referring to FIG. 3A, semiconductor wafers 100 are loaded in the bath 200 filled with the DIW 210. The semiconductor wafers 100 are supported by the semiconductor wafer supporter 230. The structure of the semiconductor wafers 100 being supported by the semiconductor wafer supporter 230 has been described above with reference to FIGS. 2A and 2B. When the semiconductor wafers 100 are loaded in the bath 200, the bath 200 is filled so that the semiconductor wafers 100 can completely soak in the DIW 210.
Referring to FIG. 3B, the DIW 210 is drained from the bath 200 through the DIW outlet 220, and nitrogen gas and IPA vapor are supplied toward the semiconductor wafers 100. The DIW 210, as marked by arrows 212 in FIG. 3B, is drained in a downward direction so that an upper part of each of the semiconductor wafers 100 is exposed. The IPA vapor supplied into the bath 200 removes any residual DIW 210 remaining on the surfaces of the semiconductor wafers 100. During the cleaning process, the semiconductor wafers 100 may move slightly, thereby possibly attaching to one another due to the surface tension therebetween. Various semiconductor wafers 100 in contact with each other are shown by points C in FIG. 3B.
As shown in FIG. 3C, the DIW 210 may remain attached between the semiconductor wafers 100. Moreover, as illustrated in FIG. 3D, the remaining DIW 210 may flow down a surface of a semiconductor wafer 100 due to gravity. This may cause the occurrence of a water mark 210′ on the surface of the semiconductor wafer 100.
Recently, the size of semiconductor wafers has increased. In particular, many semiconductor wafers are manufactured having a size greater than 200 mm. In order to batch-process a considerable number of semiconductor wafers having an increased size, with an apparatus for drying semiconductor wafers using IPA vapor, the drying process is performed using a half pitch technique where a plurality of semiconductor wafers are loaded in the apparatus so that a gap between the semiconductor wafers is very small. If the half pitch drying technique is used, semiconductor wafers may move laterally, which may cause a plurality of the semiconductor wafers to attach to one another. If adjacent semiconductor wafers attach to one another during a drying process, DIW is likely to remain on the surface of the semiconductor wafers and ultimately leave watermarks. When this happens, device malfunctions may occur.